issue_comments: 474793985

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https://github.com/pydata/xarray/issues/521#issuecomment-474793985 https://api.github.com/repos/pydata/xarray/issues/521 474793985 MDEyOklzc3VlQ29tbWVudDQ3NDc5Mzk4NQ== 20947797 2019-03-20T11:39:18Z 2019-03-20T11:39:18Z NONE

Opening the file as ds = xr.open_dataset('some_CESM_output_file.nc', decode_times=False) the time coordinate ds.time is at first simply an array of floats: <xarray.DataArray 'time' (time: 1)> array([73020.]) Coordinates: * time (time) float64 7.302e+04 Attributes: long_name: time units: days since 0-1-1 00:00:00 bounds: time_bnds calendar: 365_day standard_name: time axis: T and after decoding xr.decode_cf(ds, use_cftime=True).time returns <xarray.DataArray 'time' (time: 1)> array([cftime.DatetimeNoLeap(200, 1, 21, 0, 0, 0, 0, 3, 21)], dtype=object) Coordinates: * time (time) object 0200-01-21 00:00:00 Attributes: long_name: time bounds: time_bnds standard_name: time axis: T

The traceback of opening the file without decode_times=False complains about year 0 being outside the range of the Gregorian or Julian calendars:

traceback --------------------------------------------------------------------------- OutOfBoundsDatetime Traceback (most recent call last) ~/.conda/envs/CESM/lib/python3.6/site-packages/xarray/coding/times.py in _decode_datetime_with_pandas(flat_num_dates, units, calendar) 128 try: --> 129 ref_date = pd.Timestamp(ref_date) 130 except ValueError: pandas/_libs/tslibs/timestamps.pyx in pandas._libs.tslibs.timestamps.Timestamp.__new__() pandas/_libs/tslibs/conversion.pyx in pandas._libs.tslibs.conversion.convert_to_tsobject() pandas/_libs/tslibs/conversion.pyx in pandas._libs.tslibs.conversion.convert_str_to_tsobject() pandas/_libs/tslibs/conversion.pyx in pandas._libs.tslibs.conversion.convert_str_to_tsobject() pandas/_libs/tslibs/np_datetime.pyx in pandas._libs.tslibs.np_datetime.check_dts_bounds() OutOfBoundsDatetime: Out of bounds nanosecond timestamp: 0-01-01 00:00:00 During handling of the above exception, another exception occurred: OutOfBoundsDatetime Traceback (most recent call last) ~/.conda/envs/CESM/lib/python3.6/site-packages/xarray/coding/times.py in decode_cf_datetime(num_dates, units, calendar, use_cftime) 175 dates = _decode_datetime_with_pandas(flat_num_dates, units, --> 176 calendar) 177 except (OutOfBoundsDatetime, OverflowError): ~/.conda/envs/CESM/lib/python3.6/site-packages/xarray/coding/times.py in _decode_datetime_with_pandas(flat_num_dates, units, calendar) 132 # strings, in which case we fall back to using cftime --> 133 raise OutOfBoundsDatetime 134 OutOfBoundsDatetime: During handling of the above exception, another exception occurred: ValueError Traceback (most recent call last) ~/.conda/envs/CESM/lib/python3.6/site-packages/xarray/coding/times.py in _decode_cf_datetime_dtype(data, units, calendar, use_cftime) 93 result = decode_cf_datetime(example_value, units, calendar, ---> 94 use_cftime) 95 except Exception: ~/.conda/envs/CESM/lib/python3.6/site-packages/xarray/coding/times.py in decode_cf_datetime(num_dates, units, calendar, use_cftime) 178 dates = _decode_datetime_with_cftime( --> 179 flat_num_dates.astype(np.float), units, calendar) 180 ~/.conda/envs/CESM/lib/python3.6/site-packages/xarray/coding/times.py in _decode_datetime_with_cftime(num_dates, units, calendar) 112 return np.asarray(cftime.num2date(num_dates, units, calendar, --> 113 only_use_cftime_datetimes=True)) 114 else: cftime/_cftime.pyx in cftime._cftime.num2date() ValueError: zero not allowed as a reference year, does not exist in Julian or Gregorian calendars During handling of the above exception, another exception occurred: ValueError Traceback (most recent call last) <ipython-input-4-b14d0187112b> in <module> ----> 1 ds = xr.open_dataset(CESM_filename(domain='ocn', run='ctrl', y=200, m=1))#, use_cftime=True) ~/.conda/envs/CESM/lib/python3.6/site-packages/xarray/backends/api.py in open_dataset(filename_or_obj, group, decode_cf, mask_and_scale, decode_times, autoclose, concat_characters, decode_coords, engine, chunks, lock, cache, drop_variables, backend_kwargs, use_cftime) 392 393 with close_on_error(store): --> 394 ds = maybe_decode_store(store) 395 396 # Ensure source filename always stored in dataset object (GH issue #2550) ~/.conda/envs/CESM/lib/python3.6/site-packages/xarray/backends/api.py in maybe_decode_store(store, lock) 322 store, mask_and_scale=mask_and_scale, decode_times=decode_times, 323 concat_characters=concat_characters, decode_coords=decode_coords, --> 324 drop_variables=drop_variables, use_cftime=use_cftime) 325 326 _protect_dataset_variables_inplace(ds, cache) ~/.conda/envs/CESM/lib/python3.6/site-packages/xarray/conventions.py in decode_cf(obj, concat_characters, mask_and_scale, decode_times, decode_coords, drop_variables, use_cftime) 477 vars, attrs, coord_names = decode_cf_variables( 478 vars, attrs, concat_characters, mask_and_scale, decode_times, --> 479 decode_coords, drop_variables=drop_variables, use_cftime=use_cftime) 480 ds = Dataset(vars, attrs=attrs) 481 ds = ds.set_coords(coord_names.union(extra_coords).intersection(vars)) ~/.conda/envs/CESM/lib/python3.6/site-packages/xarray/conventions.py in decode_cf_variables(variables, attributes, concat_characters, mask_and_scale, decode_times, decode_coords, drop_variables, use_cftime) 399 k, v, concat_characters=concat_characters, 400 mask_and_scale=mask_and_scale, decode_times=decode_times, --> 401 stack_char_dim=stack_char_dim, use_cftime=use_cftime) 402 if decode_coords: 403 var_attrs = new_vars[k].attrs ~/.conda/envs/CESM/lib/python3.6/site-packages/xarray/conventions.py in decode_cf_variable(name, var, concat_characters, mask_and_scale, decode_times, decode_endianness, stack_char_dim, use_cftime) 304 for coder in [times.CFTimedeltaCoder(), 305 times.CFDatetimeCoder(use_cftime=use_cftime)]: --> 306 var = coder.decode(var, name=name) 307 308 dimensions, data, attributes, encoding = ( ~/.conda/envs/CESM/lib/python3.6/site-packages/xarray/coding/times.py in decode(self, variable, name) 417 calendar = pop_to(attrs, encoding, 'calendar') 418 dtype = _decode_cf_datetime_dtype(data, units, calendar, --> 419 self.use_cftime) 420 transform = partial( 421 decode_cf_datetime, units=units, calendar=calendar, ~/.conda/envs/CESM/lib/python3.6/site-packages/xarray/coding/times.py in _decode_cf_datetime_dtype(data, units, calendar, use_cftime) 99 'opening your dataset with decode_times=False.' 100 % (units, calendar_msg)) --> 101 raise ValueError(msg) 102 else: 103 dtype = getattr(result, 'dtype', np.dtype('object')) ValueError: unable to decode time units 'days since 0000-01-01 00:00:00' with the default calendar. Try opening your dataset with decode_times=False. 
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